· Sharks belong to a family of fish that have skeletons made of cartilage, a tissue more flexible and lighter than bone.Sharks do not have a single bone in their bodies. Instead they have a skeleton made up of cartilage; the same type of tough, flexible tissue that makes up human ears and noses.
· Sharks generally have about 45 to 50 teeth – but that’s just the "front row" teeth. They also have, on average, as many as seven replacement rows of teeth behind the front row, ready to move into place if a tooth is damaged or falls out. With all the action a shark’s mouth sees throughout its lifetime, an individual might go through as many as 30,000 teeth.
· The Swell Shark, found in New Zealand, barks like a dog.
· Sharks appeared on the fossil scene about 455 to 425 million years ago.There are about 440 species of sharks.
· Some sharks remain on the move for their entire lives. This forces water over their gills, delivering oxygen to the blood stream. If the shark stops moving then it will suffocate and die.
· Sharks have very good senses. Sometimes a shark is called “a swimming nose”, for its great sense of smell. Sharks can easily detect prey that is in the sand, as well as at night. A shark also has a remarkable sensitivity to vibrations in the water. It can feel the movements made by other animals that are hundreds of feet away. They can hear sounds from thousands of feet away. Sharks can tell the direction from where the sound is coming from, too.
· Shark ‘skin’ is made up of a series of scales that act as an outer skeleton for easy movement and for saving energy in the water. The upper side of a shark is generally dark to blend in with the water from above and their undersides are white or lighter colored, blends in with the lighter surface of the sea from below. This helps to camouflage them from predators and prey.
· While nobody seems to know the true answer, it is estimated that the whale shark, the largest shark species, can live up to 100-150 years, and many of the smaller sharks can live at least 20-30 years.
· Sharks also have a very acute sense of smell that allows them to detect blood in the water from miles away.
· Shark diet depends on the species, but most species of shark eat things like fish, crustaceans, mollusks, plankton, krill, marine mammals and other sharks.
· Sharks do not sleep the same way as humans do. They might seem as if they are sleeping but they are really just resting.
· Most sharks give birth to their babies. Only a few sharks lay eggs. Most sharks have six to twelve babies at a time, but the Hammerhead and Tiger Shark can have as many as 40 babies at a time.
· Great whites are the deadliest shark in the ocean. These powerful predators can race through the water at 30 km per hour.
· Whale sharks claim the title of largest shark species, and are also the largest species of fish in the world. The basking shark, the second largest shark (and fish), averages between approximately 22 and 29 feet/ 7 and 9 meters. Pygmy Ribbontail Catsharks are perhaps the smallest, at about 6 to 7 inches/ 17 to 18 centimeters. Other small species include the Dwarf Lanternfish and the Spined Pygmy Shark, both of which are roughly the same average size as Pygmy Ribbontail Catsharks.
· Most sharks are especially active in the evening and night when they hunt. Some sharks migrate over great distances to both feed and breed. This can take them over entire ocean basins. While some shark species are solitary, others display social behavior at various levels. Hammerhead sharks, for instance, school during mating season around seamounts and islands.
Some shark species like the great white shark attack and surprise their prey, usually seals and sea lions, from below. Species that dwell on the ocean floor have developed the ability to bottom-feed. Others attack schooling fish in a feeding frenzy, while large sharks like the whale and basking sharks filter feed by swimming through the ocean with their mouths open wide and filtering large quantities of plankton and krill.
· A shark always has a row of smaller teeth developing behind its front teeth. Eventually the smaller teeth move forward, like a conveyor belt, and the front teeth fall out.
· The bull shark is the only shark that can live in both fresh and salt water. A bull shark may have been responsible for a shark attack that happened in a creek in New Jersey back in 1916.
· Sharks' eyes are on the sides of their heads, so they have an amazingly wide sightline spanning nearly 360 degrees. Their panoramic view of the undersea world is inhibited only by two blind spots, one in front of the snout and the other directly behind the head.